This invention relates to bearing materials, and, more particularly, to a method for producing a flat stock having a bearing surface.
It is known in the prior art to produce a flat bearing material having a low friction surface of self-lubricating material such as TEFLON. U.S. Pat. No. 5,087,132, issued on Feb. 11, 1992, to Tanaka et al., and British Patent No. 1,233,103, issued on May 26, 1971, to James Victor Shepherd, are illustrative of prior art methods.
In these known methods of U.S. Pat. No. 5,087,132 and British 1,233,103 for applying a low friction bearing surface of self-lubricating material to a flat member, the TEFLON material is typically wetted and then matched to the flat material followed by pressing against the flat member. In all such methods, particular care must be taken to ensure that the mating of the low friction material and the flat surface of the backing material is very close prior to pressing and elevation to cure temperature, otherwise an uneven bearing surface can be produced or uneven bonding of the TEFLON material to the surface of the support can result. The cloth must be evenly applied to the support surface to prevent creases or irregularities being incorporated into the cloth during the pressing and heat curing steps. Additionally, the amount of resin applied must be carefully controlled to avoid excess resin forming aggregations of resin between the cloth and supporting surface on one hand, while on the other insuring that sufficient resin is present to securely bond the cloth to the flat surface. Furthermore, the pressing requires the provision of expensive pressing equipment and increases the labor costs.
The prior art and method disclosed in U.S. Pat. No. 4,258,960 does not produce flat stock. It produces a square filament wound slip sleeve liner having flat outer surfaces and inner surfaces of self-lubricating material. In this patent after the slip sleeve liner has been formed and cured its outer surfaces are machined to provide a finished sleeve of small square cross section defining a bore approximately 3/8 inches square.
All of the prior art methods are used to produce small sized components. There exists a need for a method of producing large size flat stock having a self-lubricating material bonded thereto at low cost that will have a long service life while withstanding severe stress and environmentally harsh service conditions as for example when used in expansion slip joints for bridges and roads. PA1 The problem with known methods as above described is that it is not feasible to use them to produce large sheets of flat stock. These known methods are complex, time consuming, require special tooling and as a consequence components made thereby are expensive.
A simpler, more reliable and more consistent method is thereby required for producing inexpensive flat stock material having a bonded low friction bearing surface of very even and high quality.